Wireless communication networks provide wireless data services to wireless user devices. Exemplary wireless data services include voice-calling, internet-access, and machine communications. Exemplary wireless user devices comprise phones, computers, drones, and robots. The wireless communication networks have wireless access nodes that exchange wireless signals with the wireless user devices. The wireless user devices detect wireless signals that are broadcast by the wireless access nodes, and a given wireless user device generally attaches to the wireless access node that has the strongest wireless signal. The wireless user devices continually measure and report signal strengths for wireless access points that they detect. The wireless access nodes share these signal strength reports.
The wireless access nodes have Two-Dimensional (2D) Multiple Input Multiple Output (MIMO) antenna arrays and Three-Dimensional (3D) MIMO antenna arrays. The 2D MIMO antenna arrays use horizontal beamforming to serve the wireless user devices. The 3D MIMO antenna arrays use both horizontal and vertical beamforming to serve the wireless user devices. The 3D MIMO antenna arrays are sometimes called “massive” MIMO arrays, and the massive MIMO arrays typically exhibit superior spectral efficiency over the 2D MIMO arrays. Unfortunately, the 3D MIMO antenna arrays generate significant radio interference at neighbor wireless access nodes.
The wireless access nodes maintain highly accurate clocks. The clocks are periodically synchronized with network clocks and/or Global Positioning Satellite (GPS) signals. The wireless access nodes uses their clocks to synchronize the wireless user devices. When a wireless access node loses synchronization, the ability to synchronize the wireless user devices is lost. The loss-of-synchronization may be caused by an alignment timer time-out due to a lack of user data exchanges, a GPS or clock fault, an Orthogonal Frequency Division Multiplexing (OFDM) time-slot shift, or some other synchronization condition. Unfortunately, the loss-of-synchronization generates additional radio interference at the neighbor wireless access nodes.